1. Field of the Invention
The present invention relates to an anti-vibration actuator, and in particular to an anti-vibration actuator and lens unit and camera equipped therewith for moving an image-stabilizing lens within a plane perpendicular to the optical axis thereof.
2. Description of Related Art
Published Unexamined Application JP2006-106177A describes an actuator. FIG. 6 shows the overall structure of this actuator. As shown in FIG. 6, an actuator 110 is furnished with a fixed portion 112 and a movable portion 114; the movable portion 114 is supported by three steel balls 118 to be translationally and rotationally movable with respect to the fixed portion 112. The movable portion 114 is driven by three linear motors comprising three sets of drive coils 120 and drive magnets 122.
The lines of action of the drive forces generated by these three actuators are respectively directed in the circumferential direction of a circle centered on the optical axis A of the image-stabilizing lens. Hall elements 124 for detecting the position of each of the mutually opposing drive magnets 122 are disposed on the inside of each of the drive coils 120.
In the actuator 110, rotation of the movable portion 114 is not restricted by a guide means or the like, but translational movement of the movable portion 114 is achieved by driving with the three linear motors in coordination. In addition, rotational movement of the movable portion is enabled by control of the three linear motors.
Thus an actuator not furnished with a guide means for restricting rotation of the movable portion has the advantages of a simple mechanism to support the movable portion, and of allowing rotational movement of the movable portion.
Published Unexamined Application JP2008-122531A describes an image blurring compensation device. This image blurring compensation device is furnished with 2 linear motors, and the lines of action of the drive forces generated by these 2 linear motors are respectively directed in the radial direction of a circle centered on image-stabilizing lens optical axis A.
However, the actuator described in Published Unexamined Application 2006-106177 had the problem that to increase the drive force generated by the linear motors required increasing the outside diameter of the actuator. I.e., the drive force generated by each of the linear motors was produced by the magnetic flux generated by the drive magnets 122 and the interaction of currents flowing in the shaded portion of each of the drive coils 120 of FIG. 6. It was therefore necessary to enlarge the shaded portion of each of the drive coils 120 in order to increase the drive force generated by each of the linear motors. Extending the shaded portion of each drive coil 120 requires extending each drive coil in the radial direction of the circle centered on the optical axis, creating the problem of an expanded outer diameter of the actuator as a whole.
In the actuator described in Published Unexamined Application JP2008-122531A, on the other hand, the lines of action of the drive force generated by the linear motors are directed in the radial direction of the circle, therefore the drive force can be increased by expanding each of the drive coils in the circumferential direction. Hence, in this type of actuator, an increase in drive force does not directly lead to enlargement of the actuator.
In the actuator described in Published Unexamined Application JP2008-122531A, however, the drive force from each of the linear motors is radially directed, resulting in the problem that rotational movement of the image-stabilizing lens cannot be directly controlled. This leads to an unnecessary rotational movement of the image-stabilizing lens accompanying translational movement of the image-stabilizing lens, thereby decreasing blur compensation accuracy.